On Friday 07 February 2003 04:00, G W Reynolds wrote: > I am using mprime 22.12 on a pentium 166 MMX to do trial factoring. For the > exponents currently being assigned from primenet it takes this machine > about 12 minutes to factor from 2^57 to 2^58. > > I thought I would try factoring some small exponents (under 1,000,000) from > the nofactors.zip file. I put FactorOverride=64 into prime.ini and started > mprime as usual but progress is _much_ slower, it will take about 8 hours > to factor from 2^57 to 2^58. > > Can someone tell me why the time difference is so great?
Factors (if any) of 2^p-1 are all of the form 2kp+1, so there are less candidate factors to check in any particular range as the exponent increases. FYI the exponents under 1 million have already had a lot of "extra-curricular" factoring work done on them - _all_ have had P-1 run to limits much higher than the "economic" values suggested by mprime/Prime95, many have already had extra trial factoring done, and some of the smaller ones have had substantial amounts of ECM work. I'd expect you to find _some_ factors by extending trial factoring even further, but not very many. If you have a reasonable amount of memory on your system I'd reccomend running P-1 on selected exponents just above 1 million - use the pminus1 database file to direct your work. Otherwise ECM on small exponents, or trial factoring on those exponents which have not been done "deep enough" - there are a considerable number of these in the 6M - 8M exponent range. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
